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/* @(#)z_tan.c 1.0 98/08/13 */
/******************************************************************
 * The following routines are coded directly from the algorithms
 * and coefficients given in "Software Manual for the Elementary
 * Functions" by William J. Cody, Jr. and William Waite, Prentice
 * Hall, 1980.
 ******************************************************************/
 
/*
FUNCTION
        <<tan>>, <<tanf>>---tangent
 
INDEX
tan
INDEX
tanf
 
ANSI_SYNOPSIS
        #include <math.h>
        double tan(double <[x]>);
        float tanf(float <[x]>);
 
TRAD_SYNOPSIS
        #include <math.h>
        double tan(<[x]>)
        double <[x]>;
 
        float tanf(<[x]>)
        float <[x]>;
 
 
DESCRIPTION
<<tan>> computes the tangent of the argument <[x]>.
Angles are specified in radians.
 
<<tanf>> is identical, save that it takes and returns <<float>> values.
 
RETURNS
The tangent of <[x]> is returned.
 
PORTABILITY
<<tan>> is ANSI. <<tanf>> is an extension.
*/
 
/******************************************************************
 * Tangent
 *
 * Input:
 *   x - floating point value
 *
 * Output:
 *   tangent of x
 *
 * Description:
 *   This routine calculates the tangent of x.
 *
 *****************************************************************/
 
#include "fdlibm.h"
#include "zmath.h"
 
#ifndef _DOUBLE_IS_32BITS
 
static const double TWO_OVER_PI = 0.63661977236758134308;
static const double p[] = { -0.13338350006421960681,
                             0.34248878235890589960e-2,
                            -0.17861707342254426711e-4 };
static const double q[] = { -0.46671683339755294240,
                             0.25663832289440112864e-1,
                            -0.31181531907010027307e-3,
                             0.49819433993786512270e-6 };
 
double
_DEFUN (tan, (double),
        double x)
{
  double y, f, g, XN, xnum, xden, res;
  int N;
 
  /* Check for special values. */
  switch (numtest (x))
    {
      case NAN:
        errno = EDOM;
        return (x);
      case INF:
        errno = EDOM;
        return (z_notanum.d);
    }
 
  y = fabs (x);
 
  /* Check for values that are out of our range. */
  if (y > 105414357.0)
    {
      errno = ERANGE;
      return (y);
    }
 
  if (x < 0.0)
    N = (int) (x * TWO_OVER_PI - 0.5);
  else
    N = (int) (x * TWO_OVER_PI + 0.5);
 
  XN = (double) N;
 
  f = x - N * __PI_OVER_TWO;
 
  /* Check for values that are too small. */
  if (-z_rooteps < f && f < z_rooteps)
    {
      xnum = f;
      xden = 1.0;
    }
 
  /* Calculate the polynomial. */
  else
    {
      g = f * f;
 
      xnum = f * ((p[2] * g + p[1]) * g + p[0]) * g + f;
      xden = (((q[3] * g + q[2]) * g + q[1]) * g + q[0]) * g + 1.0;
    }
 
  if (N & 1)
    {
      xnum = -xnum;
      res = xden / xnum;
    }
  else
    {
      res = xnum / xden;
    }
 
  return (res);
}
 
#endif /* _DOUBLE_IS_32BITS */

Line No.	Rev	Author	Line
1	1010	ivang
2			`/* @(#)z_tan.c 1.0 98/08/13 */`
3			`/******************************************************************`
4			`* The following routines are coded directly from the algorithms`
5			`* and coefficients given in "Software Manual for the Elementary`
6			`* Functions" by William J. Cody, Jr. and William Waite, Prentice`
7			`* Hall, 1980.`
8			`******************************************************************/`
9
10			`/*`
11			`FUNCTION`
12			`<<tan>>, <<tanf>>---tangent`
13
14			`INDEX`
15			`tan`
16			`INDEX`
17			`tanf`
18
19			`ANSI_SYNOPSIS`
20			`#include <math.h>`
21			`double tan(double <[x]>);`
22			`float tanf(float <[x]>);`
23
24			`TRAD_SYNOPSIS`
25			`#include <math.h>`
26			`double tan(<[x]>)`
27			`double <[x]>;`
28
29			`float tanf(<[x]>)`
30			`float <[x]>;`
31
32
33			`DESCRIPTION`
34			`<<tan>> computes the tangent of the argument <[x]>.`
35			`Angles are specified in radians.`
36
37			`<<tanf>> is identical, save that it takes and returns <<float>> values.`
38
39			`RETURNS`
40			`The tangent of <[x]> is returned.`
41
42			`PORTABILITY`
43			`<<tan>> is ANSI. <<tanf>> is an extension.`
44			`*/`
45
46			`/******************************************************************`
47			`* Tangent`
48			`*`
49			`* Input:`
50			`* x - floating point value`
51			`*`
52			`* Output:`
53			`* tangent of x`
54			`*`
55			`* Description:`
56			`* This routine calculates the tangent of x.`
57			`*`
58			`*****************************************************************/`
59
60			`#include "fdlibm.h"`
61			`#include "zmath.h"`
62
63			`#ifndef _DOUBLE_IS_32BITS`
64
65			`static const double TWO_OVER_PI = 0.63661977236758134308;`
66			`static const double p[] = { -0.13338350006421960681,`
67			`0.34248878235890589960e-2,`
68			`-0.17861707342254426711e-4 };`
69			`static const double q[] = { -0.46671683339755294240,`
70			`0.25663832289440112864e-1,`
71			`-0.31181531907010027307e-3,`
72			`0.49819433993786512270e-6 };`
73
74			`double`
75			`_DEFUN (tan, (double),`
76			`double x)`
77			`{`
78			`double y, f, g, XN, xnum, xden, res;`
79			`int N;`
80
81			`/* Check for special values. */`
82			`switch (numtest (x))`
83			`{`
84			`case NAN:`
85			`errno = EDOM;`
86			`return (x);`
87			`case INF:`
88			`errno = EDOM;`
89			`return (z_notanum.d);`
90			`}`
91
92			`y = fabs (x);`
93
94			`/* Check for values that are out of our range. */`
95			`if (y > 105414357.0)`
96			`{`
97			`errno = ERANGE;`
98			`return (y);`
99			`}`
100
101			`if (x < 0.0)`
102			`N = (int) (x * TWO_OVER_PI - 0.5);`
103			`else`
104			`N = (int) (x * TWO_OVER_PI + 0.5);`
105
106			`XN = (double) N;`
107
108			`f = x - N * __PI_OVER_TWO;`
109
110			`/* Check for values that are too small. */`
111			`if (-z_rooteps < f && f < z_rooteps)`
112			`{`
113			`xnum = f;`
114			`xden = 1.0;`
115			`}`
116
117			`/* Calculate the polynomial. */`
118			`else`
119			`{`
120			`g = f * f;`
121
122			`xnum = f * ((p[2] * g + p[1]) * g + p[0]) * g + f;`
123			`xden = (((q[3] * g + q[2]) * g + q[1]) * g + q[0]) * g + 1.0;`
124			`}`
125
126			`if (N & 1)`
127			`{`
128			`xnum = -xnum;`
129			`res = xden / xnum;`
130			`}`
131			`else`
132			`{`
133			`res = xnum / xden;`
134			`}`
135
136			`return (res);`
137			`}`
138
139			`#endif /* _DOUBLE_IS_32BITS */`

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